Report on Manam (Papua New Guinea) — December 1986
Scientific Event Alert Network Bulletin, vol. 11, no. 12 (December 1986)
Managing Editor: Lindsay McClelland.
Manam (Papua New Guinea) Ash emissions and rumbling; seismicity continues
Please cite this report as:
Global Volcanism Program, 1986. Report on Manam (Papua New Guinea) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 11:12. Smithsonian Institution.
Papua New Guinea
4.08°S, 145.037°E; summit elev. 1807 m
All times are local (unless otherwise noted)
Activity remained at a low level throughout December. Main and Southern Craters emitted mostly weak white to grey vapours, but brown ash-laden clouds were occasionally emitted from Southern Crater on 19, 21, 23, 28, 29, and 30 December. Deep rumbling was occasionally heard at an observation post 4 km from the summit. Seismicity showed no significant changes, with 1,000-1,500 small events recorded/day. The tiltmeter . . . continued to show a slight inflationary trend; 5.5 µrad of radial tilt have accumulated in 1986.
Geologic Background. The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1807-m-high basaltic-andesitic stratovolcano to its lower flanks. These "avalanche valleys" channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern, and western sides. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent historical eruptions, typically of mild-to-moderate scale, have been recorded since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.
Information Contacts: J. Mori and P. Lowenstein, RVO.